1. Field
This invention relates to the recovery of viscous petroleum from earth formations using an enhanced oil recovery technique. The invention more particularly relates to apparatus useful, in injection well systems to selectively provide vapor and/or liquid simultaneously to one or more formations encountered by the well bore through a single conduit.
2. Prior Art
One technique of enhanced oil recovery known as flooding involves injecting a heated fluid (usually water) into a central well to carry heat to formations in the well having viscous petroleum deposits. The heat reduces the petroleum viscosity, making it more fluid, and the injected steam and/or hot water moves the petroleum through the formations into surrounding well bores for flow to the surface.
Several United States Patents have addressed multiple formation injection utilizing heated fluids. Ronald K. Churchman U.S. Pat. No. 4,248,302 discloses completion techniques and apparatus to enhance petroleum recovery from more than one formation in a well using heated liquid. This system is operable in one or more formations in a well containing the most viscous petroleum deposits known as tar sands and utilizes injection mandrels with retrievable injection controls.
John R. Deming et al U.S. Pat. No. 4,595,057 sets forth a system and method of multiformation injection to deliver steam or hot water to two formations simultaneously. This invention requires two tubing strings for injection and does not include means for controlling injected flow.
My copending application for U. S. Patent, Serial No. 793,842, filed Nov. 1, 1985, now U.S. Pat. No. 4,646,828, discloses mandrels useful in a single injection conduit in a steam injection well to direct wet and dry steam exterior of the mandrels for flow into formations encountered by the well bore.
As different formations have widely differing characteristics, steam injection for efficient and most recovery of petroleum from a formation may require low or high heat delivery from drier steam or wetter steam and hot water. For example, a formation into which steam injection has just begun probably will require great quantities of heat from drier steam for efficient recovery. A formation which has been injected into for years may require heat in the form of great quantities of wetter steam and hot water for efficicent recovery of most viscous petroleum.